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Spatial codes in dendritic BC1 RNA.

Muslimov IA, Iacoangeli A, Brosius J, Tiedge H - J. Cell Biol. (2006)

Bottom Line: This element features a GA kink-turn (KT) motif that is indispensable for distal targeting.It specifically interacts with heterogeneous nuclear ribonucleoprotein A2, a trans-acting targeting factor that has previously been implicated in the transport of MBP mRNA in oligodendrocytes and neurons.Our work suggests that a BC1 KT motif encodes distal targeting via the A2 pathway and that architectural RNA elements, such as KT motifs, may function as spatial codes in neural cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Pharmacology, The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Health Science Center at Brooklyn, Brooklyn, NY 11203, USA.

ABSTRACT
BC1 RNA is a dendritic untranslated RNA that has been implicated in local translational control mechanisms in neurons. Prerequisite for a functional role of the RNA in synaptodendritic domains is its targeted delivery along the dendritic extent. We report here that the targeting-competent 5' BC1 domain carries two dendritic targeting codes. One code, specifying somatic export, is located in the medial-basal region of the 5' BC1 stem-loop structure. It is defined by an export-determinant stem-bulge motif. The second code, specifying long-range dendritic delivery, is located in the apical part of the 5' stem-loop domain. This element features a GA kink-turn (KT) motif that is indispensable for distal targeting. It specifically interacts with heterogeneous nuclear ribonucleoprotein A2, a trans-acting targeting factor that has previously been implicated in the transport of MBP mRNA in oligodendrocytes and neurons. Our work suggests that a BC1 KT motif encodes distal targeting via the A2 pathway and that architectural RNA elements, such as KT motifs, may function as spatial codes in neural cells.

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Somatic export codes. (A) Bulge mutant (B22) BC1 RNA (ΔU). (B) Shortening of the basal stem (S-B). Both mutations resulted in a complete loss of somatic export competence, as microinjected RNAs now remained confined to neuronal perikarya. Prolonged incubation times did not alter the observed distribution patterns. The photomicrographs show dark-field (DF; left) and phase-contrast (PC; right) images of injected neurons. Statistical analyses performed (comparison with wild-type BC1 RNA; Fig. 2) were one-way ANOVA for interval point 50 μm (P < 0.001) and Scheffe's multiple comparison post hoc analysis (P < 0.001 for both mutants). Quantitative data are presented as the mean ± the SEM of relative signal intensities along the dendritic extent. Bar, 50 μm.
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fig5: Somatic export codes. (A) Bulge mutant (B22) BC1 RNA (ΔU). (B) Shortening of the basal stem (S-B). Both mutations resulted in a complete loss of somatic export competence, as microinjected RNAs now remained confined to neuronal perikarya. Prolonged incubation times did not alter the observed distribution patterns. The photomicrographs show dark-field (DF; left) and phase-contrast (PC; right) images of injected neurons. Statistical analyses performed (comparison with wild-type BC1 RNA; Fig. 2) were one-way ANOVA for interval point 50 μm (P < 0.001) and Scheffe's multiple comparison post hoc analysis (P < 0.001 for both mutants). Quantitative data are presented as the mean ± the SEM of relative signal intensities along the dendritic extent. Bar, 50 μm.

Mentions: The medial and basal segments of the 5′ BC1 domain feature two nonhelical motifs: an unpaired U-residue at medial position 22 and a U14-C61 basal internal loop structure. U22, located within the medial helical stem (S-M) that connects the GA apical internal loop with the basal U14-C61 internal loop, is one of the most accessible nucleotides of the entire 5′ BC1 domain (Rozhdestvensky et al., 2001). Therefore, U22 is most likely not part of an A-form helical structure, but forms a bulge (B22) and may thus serve as a recognition motif (Hermann and Patel, 2000). Deletion of U22 resulted in a total loss of dendritic targeting competence (Fig. 5 A). Microinjected B22 mutant (ΔU) BC1 RNA did not enter dendrites to any substantial extent (except for a directly soma-adjacent segment of a few micrometers). These results show that bulged unpaired U22 is indispensable for proximal dendritic targeting (i.e., somatic export). It thus appears that B22 is a critical determinant of the 3D structure of the medial 5′ BC1 domain (see Discussion) and, as such, constitutes part of the somatic export code.


Spatial codes in dendritic BC1 RNA.

Muslimov IA, Iacoangeli A, Brosius J, Tiedge H - J. Cell Biol. (2006)

Somatic export codes. (A) Bulge mutant (B22) BC1 RNA (ΔU). (B) Shortening of the basal stem (S-B). Both mutations resulted in a complete loss of somatic export competence, as microinjected RNAs now remained confined to neuronal perikarya. Prolonged incubation times did not alter the observed distribution patterns. The photomicrographs show dark-field (DF; left) and phase-contrast (PC; right) images of injected neurons. Statistical analyses performed (comparison with wild-type BC1 RNA; Fig. 2) were one-way ANOVA for interval point 50 μm (P < 0.001) and Scheffe's multiple comparison post hoc analysis (P < 0.001 for both mutants). Quantitative data are presented as the mean ± the SEM of relative signal intensities along the dendritic extent. Bar, 50 μm.
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Related In: Results  -  Collection

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fig5: Somatic export codes. (A) Bulge mutant (B22) BC1 RNA (ΔU). (B) Shortening of the basal stem (S-B). Both mutations resulted in a complete loss of somatic export competence, as microinjected RNAs now remained confined to neuronal perikarya. Prolonged incubation times did not alter the observed distribution patterns. The photomicrographs show dark-field (DF; left) and phase-contrast (PC; right) images of injected neurons. Statistical analyses performed (comparison with wild-type BC1 RNA; Fig. 2) were one-way ANOVA for interval point 50 μm (P < 0.001) and Scheffe's multiple comparison post hoc analysis (P < 0.001 for both mutants). Quantitative data are presented as the mean ± the SEM of relative signal intensities along the dendritic extent. Bar, 50 μm.
Mentions: The medial and basal segments of the 5′ BC1 domain feature two nonhelical motifs: an unpaired U-residue at medial position 22 and a U14-C61 basal internal loop structure. U22, located within the medial helical stem (S-M) that connects the GA apical internal loop with the basal U14-C61 internal loop, is one of the most accessible nucleotides of the entire 5′ BC1 domain (Rozhdestvensky et al., 2001). Therefore, U22 is most likely not part of an A-form helical structure, but forms a bulge (B22) and may thus serve as a recognition motif (Hermann and Patel, 2000). Deletion of U22 resulted in a total loss of dendritic targeting competence (Fig. 5 A). Microinjected B22 mutant (ΔU) BC1 RNA did not enter dendrites to any substantial extent (except for a directly soma-adjacent segment of a few micrometers). These results show that bulged unpaired U22 is indispensable for proximal dendritic targeting (i.e., somatic export). It thus appears that B22 is a critical determinant of the 3D structure of the medial 5′ BC1 domain (see Discussion) and, as such, constitutes part of the somatic export code.

Bottom Line: This element features a GA kink-turn (KT) motif that is indispensable for distal targeting.It specifically interacts with heterogeneous nuclear ribonucleoprotein A2, a trans-acting targeting factor that has previously been implicated in the transport of MBP mRNA in oligodendrocytes and neurons.Our work suggests that a BC1 KT motif encodes distal targeting via the A2 pathway and that architectural RNA elements, such as KT motifs, may function as spatial codes in neural cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Pharmacology, The Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York Health Science Center at Brooklyn, Brooklyn, NY 11203, USA.

ABSTRACT
BC1 RNA is a dendritic untranslated RNA that has been implicated in local translational control mechanisms in neurons. Prerequisite for a functional role of the RNA in synaptodendritic domains is its targeted delivery along the dendritic extent. We report here that the targeting-competent 5' BC1 domain carries two dendritic targeting codes. One code, specifying somatic export, is located in the medial-basal region of the 5' BC1 stem-loop structure. It is defined by an export-determinant stem-bulge motif. The second code, specifying long-range dendritic delivery, is located in the apical part of the 5' stem-loop domain. This element features a GA kink-turn (KT) motif that is indispensable for distal targeting. It specifically interacts with heterogeneous nuclear ribonucleoprotein A2, a trans-acting targeting factor that has previously been implicated in the transport of MBP mRNA in oligodendrocytes and neurons. Our work suggests that a BC1 KT motif encodes distal targeting via the A2 pathway and that architectural RNA elements, such as KT motifs, may function as spatial codes in neural cells.

Show MeSH